Improvement in derricks



T. POWELL. Derrick.

No. 199,660. Patented Jan. 29, 1878.

U ITED; STA E THOMAS POWELL, on stro'cKromjoALin-oRNIA.

IMPROVEMMENTIN' DERRICKQS.

Specification forming part of Letters Patent No. 199,660, dated January29-, 1878; application filed October 9, 1877.

ing purposes.

My invention consists in so applying the ropes which sustain the boomand hoist the load that they will form a truss to stiffen and strengthenthe mast, so that the heavier the load the more perfectly will the trussbrace the mast, thus allowing me to use a light mast, as hereinaftermore fully described.

Referring to the accompanyingdrawings, let A represent a mast which isstepped in two bars or timbers, B C, which cross each other at rightangles at its base. Shoes D D are applied to the under side of the barB, while the forward end of the bar 0 is beveled to form a sled, onwhich the derrick can be moved, thus providing a broad base, withfac'ilities for moving the derrick easily.

Spliced braces connect each end of the two bars with the mast. Thesebraces are made connected, and the upper parts are folded upon the mast,while the lower parts arefolded upon their respective ends of thecross-bars.

I is an arm, which I secure upon one'side of the mast, near its top, soas to project to a distance from it. K is a boom, which is hinged to themast opposite the arm I. This boom loperate by a rope, L, one end ofwhich is attached to the boom near its outer end.

The rope then passes over a sheave or pulley,

M, near the upper end of the mast, then down over a sheave or pulley, N,in the outer end of the arm I, thence down to the base of the derrick,to which it is fastened. This arrangement of the rope causes it to serveas a truss to stiffen the mast, because any strain on the outer end ofthe boom will draw upon the cord, which will throw the weight upon themast and arm.

The hoisting-rope O has one end securedto the eye X on the under side ofthe boom, near its outer end, and passes around a pulley, P, at theextremity of the boom, thence up over a pulley, Q, at the top of themast, and down around a pulley, R, in the outer end of the arm I,outside of the pulley N, thence down around the pulley S.

Two pu1ley-blocks,T T, each of which has a hook on'its under side, arearranged to travel in the bight of the rope O on the under side of theboom, between its attachment to the eye and the pulley P. These hooksare used for attaching the blocks to the load to be lifted, which, in afarm-derrick, will usually be a netting, such as is used for unloading aheaderwagon at a single operation. In this'case one of the hooks will beattached to each side of the net. This arrangement will facilitate theoperation of attaching the net tothe hoistingblocks, so that it can behoisted, as the hooks can be separated and hooked upon the net withoutdrawing its side together. The subsequent drawing upon the rope willthen close the net upon its load. By using these two travthey can beshifted up or down upon the mast,

as desired.

Awire rope can be used for the rope L. By this arrangement I am able toconstruct a light derrick, and strengthen it so that it will lift loadsthat an untrussed derrick of this character and size would not sustain,and, as lighthaving one end attached to the eye X, and

passing around the pulley P,thence over the pulleys Q R, of the locks T'1, arranged to travel in itsbight, substantially as and forthe purposedescribed.

In witness whereof I have hereunto set my hand and seal.

THOMASPOWELL.

Witnesses: J. B.WEBsTER,

FRANK A. BROOKS.

